偽麻黃鹼
偽麻黃鹼是一種口服**擬交感神經胺**。在獸醫學中，當苯丙醇胺 (PPA) 無法取得或有禁忌症時，它主要被用作犬隻**尿道括約肌機能不全 (USMI)** 的二線治療藥物。它也可作為鼻腔去充血劑和逆行性射精的治療藥物。 > **臨床重點：** 與 PPA 相比，偽麻黃鹼在治療尿失禁方面的療效通常較差，且更容易引起不良反應（如焦躁和高血壓）。 由於它是非法合成甲基安非他命（冰毒）的前驅物，其銷售受到嚴格限制，在某些地區可能難以取得。
作用機制: Pseudoephedrine acts as an **indirect-acting sympathomimetic**. * Enters sympathetic nerve terminals → stimulates the release of endogenous **norepinephrine** from storage vesicles. * Norepinephrine binds to **alpha-1 adrenergic receptors** in the smooth muscle of the urethra and blood vessels → **vasoconstriction** and **increased urethral sphincter tone** (preventing urine leakage). * Also weakly stimulates **beta-adrenergic receptors** → positive chronotropic effects (increased heart rate) and mild bronchodilation.
各物種劑量
- As a decongestant · 1 mg/kg · PO · q8h
- For use when an antihistamine/decongestant may be useful using the pyrilamine/pseudoephedrine oral granules · ½ ounce (1 tablespoonful) per 1,000 lb body weight. May mix with feed and repeated at 12 our intervals if needed. · PO · q12h · Do not use at least 72 hours before sporting events. ARCI UCGFS CLASS 3 DRUG.
- For urinary incontinence, or as a decongestant · 0.2-0.4 mg/kg [or practically, 15-60 mg (total dose) per dog] · PO · q8-12h
- To increase urethral tone · 1.5 mg/kg · PO · two to three times a day
- For retrograde ejaculation · 4-5 mg/kg · PO · three times daily or 1 to 3 hours before semen collection or attempted breeding may be tried.
劑量為合格獸醫專業人員的臨床參考。請務必對照最新藥品仿單及個別病患確認。
給藥途徑
禁忌症
- Glaucoma
- Prostatic hypertrophy
- Hyperthyroidism
- Diabetes mellitus
- Cardiovascular disorders
- Hypertension
不良反應
- Panting
- Decreased appetite
- Lethargy
- Tachycardia
- CNS excitement
- Restlessness
- Insomnia
- Hypertension
- Arrhythmias
藥物相互作用
- Monoamine Oxidase (MAO) Inhibitors (e.g., amitraz, selegiline) · Should not be given within two weeks of receiving MAOIs; risk of severe hypertension and toxicity.
- Reserpine · Increased chance of hypertension if given concomitantly.
- Other Sympathomimetic Agents (e.g., ephedrine, phenylpropanolamine) · Increased toxicity may result; should not be administered together.
- Tricyclic Antidepressants (e.g., clomipramine, amitriptyline) · Increased chance of hypertension if given concomitantly.
監測
- Efficacy (improvement in incontinence or congestion)
- Heart rate
- CNS stimulation (restlessness, agitation)
- Appetite
過量
Overdoses of pseudoephedrine can cause **hyperthermia, mydriasis, tachycardia, hypertension, vomiting, disorientation, and seizures**. * **Toxicity Thresholds:** In small animals, adverse reactions may develop at doses of 5-6 mg/kg. Deaths have occurred at doses >10-12 mg/kg. * **Clinical Signs:** Common findings in dogs include hyperactivity, tachycardia, agitation, mydriasis, restlessness, head bobbing, and panting. Cats commonly present with tachycardia. * **Treatment:** Large overdoses should be treated with gastric evacuation (if not contraindicated). Treat supportively and symptomatically (e.g., propranolol for tachycardia). Phenothiazines are preferred to treat hyperactivity, agitation, and tremors as diazepam may worsen dysphoria. Contact an animal poison control center for further guidance.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。